Method for making a dustproof and shockless static bar



y 6, 1969 H. SCHWERINER 3,443,155

METHOD FOR MAKING A DUSTPRO OF AND SHQCKLESS STATIC BAR Filed May 18, 1966 INVENTO/Z HAROLD S C l/Wf R/IVE I? ATTORNEYS.

United States Patent 3,443,155 METHOD FOR MAKING A DUSTPROOF AND SHOCKLESS STATIC BAR Harold Schweriner, Lansdale, Pa., assignor to The Simco Company, Inc., Lansdale, Pa., a corporation of Pennsylvania Filed May 18, 1966, Ser. No. 551,015 Int. Cl. Hf 3/00 U.S. Cl. 317-2 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a static eliminator, and more particularly relates to a new and improved shockless type bar and a method for making the same.

In my prior US. Patent No. 3,120,626, there is shown a shockless type static eliminator in which a plurality of alternately arranged dielectric sleeves and conductive rings were slipped over an insulated high voltage cable. A

rigid dielectric tube or barrel was then concentrically mounted thereupon so as to encapsulate the sleeved and ringed cable. Conductive needles were then pressed through preformed longitudinally spaced holes within the tube into registering abutment with the conductive rings, and the outboard opposing points of the needles projected within an air gap of a conductive casing connected to the ground side of the high voltage source.

In this manner, a field of ionized air was created in the gap between the needles and the outer casing. Because the conductive rings, and hence the needles themselves, Were capacitatively coupled rather than directly connected to the inner wire conductor on which the high voltage was imposed, transient currents were limited should a short circuit have occurred across the gapi.e. a persons fingers or a conductive member accidentally imposed across one or more of the needles to the casing. Accordingly, the foregoing device was effective to negate shock to operating personnel as well as to minimize arcing or sparking to safe levels, particularly in explosive or inflammable environments.

However, since the conductive needles were only pressed into abutment with the rings and were held in contact therewith only as a result of the frictional engagement afforded by the insulative tubular sheath, there was a tendency for the metal-to-metal contact to deteriorate with vibration occurring during ordinary operation. Increased contact resistance would cause interior arcing in certain instances and inferior ionization in the air gap. Furthermore, loosening of the pressed metal-to-metal joint sometimes permitted the rings and sleeves to rattle and contribute to increased noise levels. Moreover, the sliding fit between the cable and the ring-sleeves and between the latter and their encapsulating tubular sheath yielded surface separations Within which dust and chemical particles could collect. Lastly, there was produced some inetficiences in assembling the sliding fit barrel-ring-sleevecable arrangement and in registering the needles with the rings, especially in making the static bars to length.

It is therefore an object of this invention to provide a dust-free integrally-formed shockless static bar in which 3,443,155 Patented May 6, 1969 the needles and their supporting sleeves are all rigidly connected together.

Another object of this invention is to provide a shockless static bar which employs an integrally-molded barrel.

Still another object of this invention is to provide an integrally molded shockless static bar that can be conveniently cut to length and assembled with minimum eiTort for any custom-made construction.

Yet another object of this invention is to provide a method for fabricating a dustproof and shockless static eliminator affording a maximum strength construction without any likelihood of rattling of component parts.

A still further object of this invention is to provide a method for fabricating a new and improved shockless static eliminator which will provide maximum electrical contact.

Yet a further object of this invention is to provide a shockless static eliminator which is always easily kept clean and which can be operated in a dusty atmosphere without any likelihood of short circuiting developing due to accumulations of dust or other foreign matter.

Other objects of this invention are to provide an improved device and method of the character described which is easily and economically produced, sturdy in construction, and both highly effective and etficient in operation.

With the above and related objects in view, this invention consists of the details of construction and combination of parts as will be more fully understood from the following detailed description when read in conjunction with the accompanying drawing, in which:

FIGURE 1 is a top plan view of a new and improved shockless static eliminator embodying my invention.

FIGURE 2 is a sectional view taken along lines 22 of FIGURE 1.

FIGURE 3 is a sectional view taken along lines 3-3 of FIGURE 2.

FIGURE 4 is a sectional view taken along lines 44 of FIGURE 2.

FIGURE 5 is a sectional view taken along lines 5-5 of FIGURE 2.

FIGURE 6 is a perspective view, and partly broken away, showing the method for integrally molding the body of the shockless static eliminator.

Referring now in greater detail to the drawings in which similar reference characters refer to similar parts, the instant invention comprises a plurality of integrally formed conductive discharging elements, generally designated as A, which are molded in longitudinally-spaced coaxial disposition within an insulative tubular barrel B. An insulated cable C is concentrically supported within the barrel B, and the barrel itself is further mounted within a conductive casing D which is both insulated and air spaced from the discharging elements A. A high voltage generator source G is connected across the conductive casing D and the inner conductor of the cable C whereby the discharging elements A are each capacitatively coupled to the inner conductor of the cable C and create an ionizing field in the air gap between the discharging points and the conductive casing D. By virtue of the capacitative coupling of the discharging elements A with the high voltage cable C, transient currents are so limited that minimal arcing and/or shock would occur should accidental shunting occur between any of the discharging elements A and the conductive casing D.

The discharging elements A are each fabricated from a length of stainless steel wire, for example,16 gage, which is wound in the form of a pigtail having a coiled sleeve portion 12 and a needle portion 14 continuous therewith and extending radially from one end. The inside diameter of the sleeve portion 12 is such that it will slidably receive the outer diameer or exterior covering of the particular high voltage cable C employed. Adjacent loops of the sleeve portion 12 abut one another so as to define a closed wall cylindrical collar. The terminal point of the needles are conically ground to a sharp tip.

In constructing the barrel B, the sleeves 12 of the discharging elements A are axially inserted upon a mandrel 16 with a spacer ring 18 incorporated between adjacent sleeves. The spacer ring 18 is molded of an acrylonitrilebutadiene-styrene copolymer, known as ABS, and each is of an identical length so that the discharging elements A will be uniformly spaced from each other. Longitudinal flutes 19 on the periphery of the ring 18 define recesses within which the plastic resin to be used in forming the barrel B will fill during molding, as will now be described.

Referring to FIGURE 6, the mandrel 16 together with its alternately-arranged abutting sleeves 12 and rings 18 is laid within an elongated semi-cylindrical mold cavity 20 contained in fixed platen 21 of injection mold E. The outside or ribbed diameter of the ring 18 is somewhat larger than that of the sleeves 12, and the periphery of the ribs is complementary to the diameter of the mold groove 20. The needle points 14 are received within longitudinally spaced complementary pinholes 22 downwardly extending from the groove 20 into the body of the mold 'E. A runner or gate 24 is laterally spaced from the main cavity groove 20 in platen 21 and communicates with the mold cavity through regularly spaced sprues 26. Of course, the injection mold E includes an upper platen 27 which is complementary with stationary lower platen 21 and maintained in reciprocable alignment therewith by conventional guide pins (not shown). ABS plastic resin is injected through main sprue orifice 28 in the usual manner to form an insulated tubular sheath 30 about the sleeves 12 of the discharging elements A. The spacers 18 prevent spreading of adjacent coils or loops of the sleeve portions 12 which would otherwise occur as a result of the plastic molding pressure. When the thermocompression plastic composition has set, the spacers 18 will also be retained in the tubular sheath 30 and fixed in position by the now plastic filled fiutes 19.

The now completed barrel B is cut to length and inserted within end collars 32 and 34 preparatory to insertion within the outer conductive casing D. Each of the end collars 32 and 34 may be molded of an acrylic resin, for example, and has a counterbored portion 35 complementary with the sheath 30 for receiving the ends of the barrel B. Collar 32 has a blind bore 33 within which the end of the cable C abuts. Collar 34 has a through bore 36 into which the cable C passes and then through the entire barrel B. A central spacer collar 38 may be utilized to adjoin the adjacent ends of a pair of longitudinally contiguous barrels B and provide peripheral support against undue fiexure of a single long barrel.

The cable C may be any conventional wire conductor 40, which is preferably stranded copper, and having a polyethylene jacket 42 with an outer cover 44 of vinyl plastic, for example. The distal end of the cable C has a cap 45 melted about the normally bare end of wire conductor to provide additional protection. The cable C is inserted through the barrels B and the two collars 34 and 38 until the end abuts blind bore 35 of collar 32. Screw 46 passes through the neck portion of collar 34 and secures the cable C in position, the screw 46 being preferably plastic, such as nylon.

The outer conductor member D, in the preferred embodiment, comprises a tubular sheet metal casing made of a suitable electrically conductive material such as brass. A plurality of circular apertures 50 are cut or formed in the casing and are longitudinally spaced from each other at regular intervals at diametrically opposed portions of the cylindrical wall. The circular apertures 50 are on the same centers as the points of the needles 14 so that 4 the latter will respectively project concentrically therewithin.

The barrels B and their enclosed cable C together with the collars 32, 34 and 38 are assembled Within the outer casing D so that the points of the discharging elements A are aligned centrally within the respective apertures 50. In this regard, it is to be noted that the medial collar 38 has slots 39 at each end to orient the needles 14 of adjacent barrels B in a common plane. Screws 48 and 52 pass through threaded holes at the ends of the casing D into engagement with the base of the necks of the end collars 32 and 34. Longitudinal adjustment is afforded for registering the needles 14 with the apertures 50 by virtue of the width of the collar necks.

The high voltage source G which may be an AC. or DC. generator having an output from 5000 to 15,000 volts, now has its hot end connected to the wire conductor 40 and its grounded end to casing D at screw 48. Each of the needles 14 is now capacitatively coupled to the conductor wire 40 through the coiled sleeve portion 12. No direct electrical contact is made between the discharging elements A to either the conductive casing D or the inner wire conductor 40. The capacity between each sleeve 12 and the central conductor may be in the range of from 3 to 10 micromicrofarads which is sufliciently small to eliminate any shock or .arcing by virtue of transient currents when an object is shorted across the needles 14 to the casing D. However, the capacity is sufficient to afford a high degree of air ionization within the circular apertures.

The provision of making the discharge elements A as an integrally wound pigtail always assures continuous electrical and physical contact of the needles 14 with the sleeves 12. Molding of the discharge elements A in positive disposition within the plastic insulator sheath 30 yields a high degree of uniformity and precision in spacing as Well as a rigid construction which is well adapted for flexibility in assembly. Furthermore, the molded encapsulation prevents any possibility of dust collection at critical surfaces.

Although this invention has been described in considerable detail, such description is intended as being illustrative rather than limiting since the invention may be variously embodied, and the scope of the invention is to be determined as claimed.

What is claimed is:

1. A dustproof shockless static eliminator comprising a plurality of discharging elements, each including a cylindrical sleeve portion and a needle portion integral therewith and outwardly extending therefrom, each of said integral sleeve and needle portions being formed of a single continuous wire element would into helical configuration with substantially abutting coils and terminating at one end in a point continuous therewith and radially oriented substantially normal to the axis thereof,

a barrel member including an insulative tubular sheath integrally molded about the sleeve portions of said discharging elements and encapsulating said sleeve portions in longitudinally spaced disposition from each other with the needle portions projecting radially from the periphery of said sheath and defining a common plane, said insulative tubular sheath being of a resinous composition and integrating all of said discharging elements within the barrel member,

a cable having a central wire conductor jacketed within a dielectric skin and extending coaxially through said barrel member,

a conductive casing longitudinally coextensive with said barrel member insulated therefrom and adjacently air-spaced from the points of said discharging elements, and

means for applying a high voltage across the wire conductor and said conductive casings whereby the sleeves of said discharging elements are capacitively coupled with the wire conductor so that an ionizing field is created in the air gap between the conductive casing and the points while afiording an essentially shockless and current limited operation in the event of an accidental shunt thereacross.

2. The invention of claim 1 wherein said outer conductive casing is cylindrical in configuration and having a plurality of longitudinally spaced circular apertures in the wall thereof with center-to-center spacing identical to that of the needles, annular collars for supporting the ends of said barrel within the casing, and means to longitudinally adjust said barrel with respect to said casing so that the needle points register with the centers of said apertures.

3. The invention of claim 2 including a medial collar for supporting the center portion of said barrel.

6 References Cited UNITED STATES PATENTS 1,841,323 1/1932 Chapman 317-2 5 2,083,478 6/1937 Sim-ons 317-2 2,163,294 6/1939 Simons 317-2 2,866,923 12/1958 Herbert 317-2 3,120,626 2/1964 Schweriner 317-2 3,162,787 12/1964 Hanscom et a1. 317-2 JOHN F. COUCH, Primary Examiner.

W. M. SHOOP, JR., Assistant Examiner. 

